This non-provisional application claims priority under 35 U.S.C. xc2xa7119(a) on Patent Application No. DE 101 46 959.4 filed in Germany on Sep. 24, 2001, which is herein incorporated by reference.
1. Field of the Invention
The invention relates to a night vision device and method for vehicles, the night vision device including a radiation device for generating infrared radiation, a detection device for receiving an infrared image, wherein the detection device works together with the radiation device, and a display device for visual display of the infrared image for the vehicle driver.
2. Description of the Background Art
Known from EP 0 479 634 B1 is a radiation device consisting of a light source that has a broadband spectrum and radiates in the visible and near infrared spectral region. A night vision device for vehicles is based on a headlight system. A filter is placed in front of a light source of the headlight in the direction of light emission, and in an operating position that intercepts the light beam, which has the effect that only the infrared portion of the light beam is transmitted and radiated in the direction of a visual field located in front of the vehicle. A resulting infrared image of the visual field in front of the vehicle can be received by a detection device, that is preferably embodied as a CCD camera, is further processed, and visually displayed by means of a suitable subsequent display device, preferably arranged in the region of the windshield. In this way the driver can be provided with an expanded visual field whose depth is greater than the visual field generated by the light source in the visible region.
A disadvantage of the known night vision device is that, in addition to the light source, a filter is required that filters out the infrared radiation for transmission in the direction of the visual field. The use of light-emitting diodes with a narrow spectral range is known as an alternative, so that additional filtering is not required. Such known light-emitting diodes are customarily operated continuously with constant emitted power.
It is therefore an object of the present invention to further develop a night vision device for vehicles such that the effectiveness of the radiation emission is improved.
To attain this object, the night vision device has a semiconductor radiation source in the radiation device that can be controlled such that the infrared radiation is emitted in a discrete-time fashion.
The special advantage of the invention is that the discrete-time behavior of the radiated signal makes possible a temporal weighting of the radiated power. This temporal weighting achieves a temporal concentration of the maximum radiated power, so that a reduction of the average radiated power occurs in spite of a relatively high maximum radiated power. This advantageously results in a higher peak radiated power that can be used to generate the infrared image in comparison to continuous operation. On the other hand, it results in a significant reduction in the average radiated power, so that the health hazard resulting from radiation in the eye can be reduced for persons coming toward the vehicle.
In accordance with a particular embodiment of the invention, the semiconductor radiation source can be controlled such that the infrared radiation is emitted in the form of a periodic pulse of radiation. It is advantageous for the radiating device to operate in a pulsed mode, which is easy to accomplish by appropriate control of the semiconductor radiation source.
In a further embodiment of the invention, the pulse width of the radiation pulse is less than {fraction (1/10)} of the cycle time, so that the radiated energy emitted is concentrated into a relatively short time interval. In an advantageous manner, the average radiated power can be significantly reduced in this way, however, this does not entail any degradation of the quality of the infrared image.
In accordance with a further embodiment of the invention, the semiconductor radiation source can be controlled synchronously with the detection device, so that detection of the radiation emission can only take place during the time interval of the radiation emission.
In accordance with a further embodiment of the invention, an additional infrared sensor is provided that receives the infrared radiation from an oncoming vehicle. As a function of the presence of such an infrared radiation signal, the operation of both the semiconductor radiation source and the detection device can be modified in such a way that the next radiation pulse can be emitted and detected with a temporal offset. In this way, the radiated infrared signal transmitted from the oncoming vehicle can be prevented from interfering with or altering the measurement result of the detection device.
In accordance with a further embodiment of the invention, the pulse pattern transmitted by the semiconductor radiation source can be altered as a function of the presence of an infrared radiation signal from an oncoming vehicle. For example, the infrared sensor that detects the infrared radiation from the oncoming vehicle can be connected to a control unit that analyzes the pulse pattern of the oncoming vehicle and changes the pulse pattern of the semiconductor radiation source as a function thereof so that no mutual interference can arise.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.